Age-related changes in the ovalbumin gene of the Japanese quail.

Northern hybridization studies showed that the level of ovalbumin mRNA decreases in the oviduct of the Japanese quail after adulthood. In order to find out if this is due to changes in the conformation of the chromatin containing the promoter region of the gene, nuclei of the oviduct of young, adult and old birds were digested by DNaseI and micrococcal nuclease (MNase). Southern hybridization with the labelled promoter showed that this region is less sensitive to the two enzymes in the old birds. Both the endonucleases recognized the same hypersensitive sites. The results indicate that the chromatin containing the promoter is present in an open conformation in adult birds. Gel mobility shift assay using a 20-mer dsDNA containing the CAAT-box and nuclear extract of oviduct shows the presence of trans-acting factors that bind to this region. The levels of these factors are lower in old birds. This may be the reason for the lower expression of the gene in old birds.